import java.io.*;
import java.nio.*;
import java.nio.channels.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class WindowFileLock extends JFrame implements ActionListener{
    JTextArea text;
    JButton button;
    File file;
    RandomAccessFile input;
    FileChannel channel;
    FileLock lock;
    WindowFileLock(File f){
        file = f;
        try{
            input = new RandomAccessFile(file,"rw");
            channel = input.getChannel();
            lock = channel.tryLock();
        }
        catch (Exception exp){}
        text=new JTextArea();
        button = new JButton("读取一行");
        button.addActionListener(this);
        add(new JScrollPane(text),BorderLayout.CENTER);
        setSize(300,400);
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    public void actionPerformed(ActionEvent e){
        try{
            lock.release();
            String lineString=input.readLine();
            text.append("\n"+lineString);
            lock=channel.tryLock();
            if(lineString==null)
                input.close();
            }
            catch(Exception ee){}
    }
}
